Properly report errors about unbound ERT test symbols.

Assertions should only be used to check internal consistency within a
package, not to check arguments passed by callers.  Instead, define
and use a new error symbol.

* lisp/emacs-lisp/ert.el (ert-test-unbound): New error symbol.
(ert-select-tests): Use it.

* test/lisp/emacs-lisp/ert-tests.el (ert-test-select-undefined): New
unit test.

* etc/NEWS: Document new behavior.

1 files changed, 7 insertions, 2 deletions

diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index c5701328704..da14b93d1bf 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -1012,7 +1012,8 @@ contained in UNIVERSE."
                           universe))))
     ((pred ert-test-p) (list selector))
     ((pred symbolp)
-     (cl-assert (ert-test-boundp selector))
+     (unless (ert-test-boundp selector)
+       (signal 'ert-test-unbound (list selector)))
      (list (ert-get-test selector)))
     (`(,operator . ,operands)
      (cl-ecase operator
@@ -1020,7 +1021,9 @@ contained in UNIVERSE."
         (mapcar (lambda (purported-test)
                   (pcase-exhaustive purported-test
                     ((pred symbolp)
-                     (cl-assert (ert-test-boundp purported-test))
+                     (unless (ert-test-boundp purported-test)
+                       (signal 'ert-test-unbound
+                               (list purported-test)))
                      (ert-get-test purported-test))
                     ((pred ert-test-p) purported-test)))
                 operands))
@@ -1059,6 +1062,8 @@ contained in UNIVERSE."
         (cl-remove-if-not (car operands)
                           (ert-select-tests 't universe)))))))
 
+(define-error 'ert-test-unbound "ERT test is unbound")
+
 (defun ert--insert-human-readable-selector (selector)
   "Insert a human-readable presentation of SELECTOR into the current buffer."
   ;; This is needed to avoid printing the (huge) contents of the